In the fortnight after the Supreme Court’s oral arguments in two same-sex-marriage cases, half a dozen senators announced they had changed their minds to support the right of gays and lesbians to wed.

The wave of turnabouts a month ago was important because it reinforced the notion that elected politicians were hurrying to get right with a seismic shift in public opinion — no matter what the justices decide to do.

But on a more tangible level, the fact that 54 senators now back marriage equality doesn’t have much real meaning. That’s simply because legislation to universalize gay marriage is nowhere near the realm of possibility.

That said, the size of that bloc could prove decisive for the fate of two measures that may show life this year.

If the justices rule, as the arguments signaled they might, and strike down a central section of the 1996 Defense of Marriage Act — the part that, in effect, prevents federal agencies from recognizing same-sex marriages in states where they’re legal — it’s a sure bet that culturally conservative Republicans will begin pushing replacement legislation. But those 54 votes would be more than sufficient to prevent such a bill from ever getting through the Senate filibuster starting gate.

More important than that defensive block for many in the gay rights community is the potential help the 54 could give legislation banning most bias against homosexuals on the job. The Employment Non-Discrimination Act would extend federal employment discrimination protections under the 1964 Civil Rights Act to sexual orientation.

Which is why proponents of the bill expressed so much worry and annoyance Monday on the news that Sen. Rob Portman of Ohio, the very first GOP senator to endorse marriage equality, was not ready to make the ideologically consistent leap to endorse legislation protecting gays from discrimination in the workplace.

“I totally support the concept,” Portman said at a Monday night event hosted by BuzzFeed and reported on by #WGDB blogger Meredith Shiner, because “there should be no discrimination and there ought to be a law in place.”

But Portman then offered two rationales for his hesitance on ENDA. They were even more troublesome to supporters than the fact that their newest and most potentially powerful GOP ally was wavering. He said enactment of the current version would lead to too many new lawsuits (something that could be said of essentially any civil rights expansion) and that it would infringe on the First Amendment rights of religious groups opposed to homosexuality (even though the bill includes a section explicitly exempting such religious organizations from having to comply).

Portman’s open wavering suggests that, one year after President Barack Obama announced his own election-year conversion to supporting gay marriage, the political momentum is neither as intense nor as one-directional as it might appear. Of the 166 sponsors of ENDA in the House, for example, only three are Republicans: Florida’s Ileana Ros-Lehtinen, Pennsylvania’s Charlie Dent and New York’s Richard Hanna.

This isn’t to label the bill a nonstarter. Its prospects have probably never been better during the 40 years it’s been kicking around the Capitol. If the Supreme Court not only strikes down DOMA but also sweeps aside same-sex marriage restrictions in California and elsewhere, such historic decisions could spur overwhelming congressional interest in granting gay people civil rights at work to complement their new rights in their personal lives.

Defeats in those cases, or even more muddied results, would prompt gay rights advocates to redouble efforts to get out of Congress some of the advances denied by the courts — and to do so before the 2014 midterm elections.

Democratic Sen. Tom Harkin of Iowa has made ENDA the top social policy objective of his final two years in the Senate, and as chairman of the Health, Education, Labor and Pensions Committee, he’s on course to move the measure in the next few months. The dozen Democrats on the panel are so far joined by at least one Republican, Mark S. Kirk of Illinois, who is the only other GOP senator backing gay marriage at the moment.

Sen. Susan Collins of Maine, who’s a safe bet to win a fourth term next year if she avoids a conservative primary challenger, hasn’t backed same-sex marriage but is nonetheless the only GOP co-sponsor of ENDA besides Kirk.

Two others who have signaled a not-quite-there-yet approach to gay marriage, Republican Lisa Murkowski and Democrat Mary L. Landrieu, are seen by some advocates as persuadable on matters of civil rights.

If those votes fall into place, and Portman’s wavering is overcome, the decisive ballot to break a filibuster could rest with Mark Pryor of Arkansas. At the moment, he stands as the Democrat in the most re-election trouble next year, and his recent votes against gun control and his party’s budget show that he’s hoping to win by hewing to a centrist line.

But there’s a sliver of Pryor’s life story that suggests he might do the unexpected. He was a 33-year-old state legislator seriously ill with a rare form of cancer back in 1996 — so sick that his father, David Pryor, was at his bedside in Little Rock rather than his desk in the Senate the only time ENDA ever made it to the floor.

The bill was defeated by a single vote because of the elder Pryor’s absence.